1. Field of the Invention
The present invention relates to oil well drilling. More particularly the present invention relates to an apparatus utilized on a drill string so that when sufficient force is exerted on the apparatus the apparatus shifts and jars loose a tool that may be stuck at the bottom of the bore hole.
2. General Background
In the process of drilling oil wells, which is usually accomplished with the use of a drill bit at the end of a continuous plurality of sections of drill pipe, called the "drill string" many tools are utilized at the end of the string in order to accomplish various tasks. Often times, during the use of these tools, a tool may become stuck or lodged within the drill bore, and must be retrieved in order to continue the drilling process. This retrieval is accomplished by the use of some type of grabbing apparatus at the end of the drill string in combination with a jarring tool.
As known in the art, a jarring tool is an apparatus which when utilized in conjunction with the drill string has either a mechanical or other type of latch engaged in the tool body, so that when sufficient force is placed on the string, the tool body is jarred loose, and when the string is encountered by the jarring motion of the tool body, oftentimes this will result in a unsticking of the tool, and therefore subsequent retrieval.
Of course, this type of jarring tool must work within the confined space of the drill string, and therefore due to this factor, there is oftentimes a malfunctioning of the mechanical latching mechanism in the present state of the art. In addition, because many state-of-the-art tools have a plurality of latching fingers around the circumferential wall of the tool body, force on the tool body is placed between the fingers and the tool body, and therefore is not evenly distributed around the wall of the tool.
For example, U.S. Pat. No. 4,889,198 issued to Buck entitled "Drilling Jar Latch", discloses a drilling jar latch tool which, as seen in the figures, particularly FIGS. 4, 5, and 6, a plurality of fingers attached to the interior wall of the tool body have tooth projections engaged into a continuous channel within the mandrel of the tool. Because of the flexion of the finger on the wall of the body, this would allow the mandrel to slip to engage and disengage during use of the tool. This particular arrangement requires that six different mechanical fingers operate in unison in order to have the proper operation of the tool. Therefore, this tool is susceptible to failure. Other patents have been granted in this field, some of the more relevant being the following:
______________________________________ U.S. PAT. NO. TITLE INVENTOR ______________________________________ 3,853,187 Duplex Hydraulic- Sutlif et al. Mechanical Jar Tool 4,688,649 Mechanical Drill String Jar Buck 4,889,198 Drilling Jar Latch Buck 4,694,917 Mechanical Jarring Devices Heidemann et al. For Use in Drilling 2,059,540 Oil Well Jar Stephan 2,591,130 Jar Brown et al. 2,008,743 Jar Black 2,978,048 Bumper Safety Joint Walker 2,051,911 Rotary Jar Siracusa 1,978,847 Rotary Jar Spang 1,885,043 Rotary Jar Beck. ______________________________________
In each case of the patents listed above in addition to the '198 patent to Buck, each of these require the external finger mechanisms operating in conjunction with the movable mandrel and are all susceptible to the problems encountered in the Buck patent.
One of the most important needs in workover well work is the ability to achieve and maintain circulation in hole. Adequate circulation is important for the following reasons:
1) it is needed to wash sand or any other material that may be causing a bridge down hole;
2) it is needed to keep pressure down hole without being blown out of the hole (mud density is varied to achieve the proper pressure down hole--without adequate circulation, the mud density cannot be changed quickly enough to prevent being blown out of the hole);
3) it is needed to keep materials moving up hole, thus keeping tools from getting stuck going in or coming out of the hole;
4) it is needed to allow the setting of hydraulic tools on the work string; hydraulic releasing tools are sometimes set below jars and accelerators to allow the jars or accelerators to be extracted from the hole if the need should arise by "pumping off" (pumping a steel ball down through the string and tools to activate the releasing tool and allow all tools and the string above the releasing tool to be removed from the hole).